can: rework the table lookup code in can_dlc_to_bytes

Rework the can_dlc_to_bytes table lookup code in a way that allow the
compiler to guess the resulting output and somehow fix the build
warning:

zephyr/drivers/can/can_nxp_s32_canxl.c:757:9: warning:
'__builtin___memcpy_chk' forming offset [16, 71] is out of the bounds
[0, 16] of object 'frame' with type 'struct can_frame' [-Warray-bounds]
 757 | memcpy(frame->data, msg_data.data, can_dlc_to_bytes(frame->dlc));

where the compiler detects that frame->data is 8 bytes long but
can_dlc_to_bytes could return more than that.

Can be reproduced with:

west build -p -b s32z270dc2_rtu1_r52 \
	-T samples/net/sockets/can/sample.net.sockets.can.one_socket

Suggested-by: Martin Jäger <martin@libre.solar>
Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
(cherry picked from commit 4856fd4c)